B. RANGES OF INFANT MORTALITY BY REGION Year for year, the most hazardous period of life is infancy. Birth injuries, congenital malformations, and the lack of maturity in the development of the infant often take their toll shortly after birth. In addition, the infant is exposed to a new environment and is subjected to infections and problems of infant feeding and care. Mortality of infants is frequently regarded as an index of sanitation applicable to many countries.

On a worldwide basis, the range of the death rate during the first year of life varies considerably. The infant mortality rate for most of the western countries has declined to a relatively low level, but it is still high in many of the other countries. If complete data were available, the range of infant mortality rates would undoubtedly be greater than shown by the black areas and recorded figures on the accompanying chart. For each of the bars shown, the figure at the base of the black section is the lowest reported mortality rate for any country in that region, and the numeral at the top of the bar is the highest reported for any country in the region. Reported rates from other countries fall between these two extremes.

C. CHILD MORTALITY UNDER 5 YEARS OF AGE BY REGION

After the first year of life, the death rate drops sharply among young children in economically developed areas. However, mortality rates continue at a relatively high level after infancy in many countries. Thus, deaths of children from birth to 5 years of age as shown by the black area on each bar graph, range from one-third to twothirds of the crude deaths at all ages reported in various countries in Africa, Asia, Middle and South America.

D. LIFE EXPECTANCY OF WORLD POPULATION

The death rate is a measure of population loss. It reflects the health of the population, but it is also affected by the age composition of the population since the risk of death is higher during the early and later periods of life.

An overall index of mortality which is adjusted for the differing age composition of the population is the life expectancy at birth. This figure is based on current mortality rates and indicates the number of years, on an average, which a baby born today may be expected to live.

Of a total 2,790 million population of the world, 801.3 millions or 28.7 percent have an estimated average life expectancy at birth of 50 years; 278.5 million or 10 percent, between 50 and 64 years; and 713.9 million or 25.6 percent, 65 years or more. For more than a third of the world's population, 996.3 millions, data are insufficient to make an estimate.

Since mortality data are not good enough to compute satisfactory life tables for most countries, many computed values used to derive this chart are questionable. However, they do indicate the magnitude of the problem for about 65 percent of the world's population. For the remaining 35 percent, although statistics are unknown, under existing disease conditions the chances of survival to old age are poor.